Packet dissemination in a wireless network performing distributed beamforming

ABSTRACT

Embodiments for providing for dissemination of packets in a network performing distributed beamforming are generally described herein. In some embodiments, distributing packets from nodes in a squad local area network using a first waveform to beamforming nodes, providing scheduling to a long link interface for delivering a stream of packets free of scheduling conflict and distributing a copy of the packets from a long link interface based on the provided scheduling and using a second waveform, the first waveform being different from the second waveform.

GOVERNMENT RIGHTS

This invention was made with Government support under Contract NumberW911QX-12-C-0039. The Government has certain rights in this invention.Contract #.

BACKGROUND

Transmit beamforming relies on coherent transmission by spatiallyseparated antennas forming constructive interference at the intendedreceiver. These spatially diverse antennas may be part of an array,multiple-input and multiple-output (MIMO) system or, separate wirelessnodes. In the latter case, nodes during beamformed transmissions obtainthe packet and a referenced time, common to all, to begin sending.

It is often assumed that nodes are within one-hop, or that a timedivision multiple access (TDMA)-based MAC schedules the beamformedtransmission immediately after dissemination. Reliance on TDMA MAC withscheduling of long link transmission in same round as packetdissemination means scheduling is not used for State-of-the-art datadissemination and scheduling on the beamformed link relies on TDMA-basedsolutions in which a common schedule is established to deliver copies ofthe original single-sourced packet to beamforming nodes. Packets aresent on the beamformed link immediately after in-network dissemination,thus obviating the need for scheduling. Perfect communications andone-hop networks are generally assumed. Works that have consideredmultiple-hop networks use a clustering solution to reduce the problem tothat of one-hop networks.

However, if more than one hop is involved, dissemination means nodesreceive a copy of a packet at different times. The network cannot waitfor nodes to receive one packet and then transmit on the uplink withinthe same round. Further, the uplink pipe is to be kept full. Packets areto be sent out on uplink at same time by nodes participating indistributed beamforming and dissemination failure is not a cause ofconflict/interference.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates distributed beamforming according to an embodiment;

FIG. 2 illustrates a graph of a network of nodes wherein an uplinkdissemination process is used according to an embodiment;

FIGS. 3 a-f illustrates a downlink dissemination process according to anembodiment; and

FIG. 4 illustrates packet scheduling in a wireless network performingdistributed beamforming according to an embodiment.

DETAILED DESCRIPTION

The following description and the drawings sufficiently illustratespecific embodiments to enable those skilled in the art to practicethem. Other embodiments may incorporate structural, logical, electrical,process, and other changes. Portions and features of some embodimentsmay be included in, or substituted for, those of other embodiments.Embodiments set forth in the claims encompass available equivalents ofthose claims.

A beamforming interface is referred to as the “Long Link” because it mayhave a long range. Embodiments described herein include two packetdissemination processes and a packet scheduling technique intended tomaximize the beamformed Long Link capacity for a Squad Local AreaNetwork (SLAN) or the Squad network. The nodes disseminate copies of theoriginal packet via Squad local area network (LAN).

The first dissemination process distributes copies of the same packet tobeamforming nodes and the second dissemination process ensures nodesreceive packets from the Long Link. The scheduling according to anembodiment delivers a stream of ordered and time synchronized packets tothe Long Link module. The SLAN dissemination processes converge in lessthan 2 seconds and reach non-partitioned nodes.

FIG. 1 illustrates distributed beamforming 100 according to anembodiment. In FIG. 1, squad nodes 110 send the same signal/packet 112from one source. At the intended destination 120, constructiveinterference occurs resulting in mutual reinforcement to produce a wave130 with an additive amplitude based on the amplitudes of the individualwaves 112. Everywhere else, destructive interference occurs resulting incancellation of each of the individual waves thereby evading detectionand interception.

Thus, FIG. 1 shows that squad nodes 110 coherently send (beamform) thesame packet to a faraway destination 120. The beamforming interface isreferred to as the Long Link interface 140 because it has a long range.In order to successfully beamform, the squad nodes 110 obtain the samecopy of the packet before the squad nodes 110 attempt to transmitcoherently. The squad nodes 110 disseminate copies of the originalpacket via Squad Local Area Network (SLAN) or the Squad network 114. TheSquad network interface and the Long Link interface are on differentwaveforms, i.e., different frequencies, different modulation schemes,etc. In effect, this means the SLAN and Long Link may be used at thesame time because they will not interfere. Deconstructive interferenceis present at the adversary nodes 150.

FIG. 2 illustrates a graph 200 of a network of nodes wherein an uplinkdissemination process is used according to an embodiment. In FIG. 2, 8nodes 210-24 are shown in the SLAN network 230. According to anembodiment, a dissemination process is iterative by nature. As one node,e.g., node 6 220, completes the process and decides to become aforwarder or not, its neighbors, e.g., node 7 222 and node 8 224, mayrun the process again to take those changes into account. This maychange output of the process, which may modify the process output of aneighbor, and which may propagate changes to the output of other nodes.The process is considered to have converged when the output of theprocess remains the same for each iteration for the nodes. The time toconvergence is the time between when the nodes start up and when thenodes reach their final output.

A source-independent MultiPoint Relay (MPR) process computes a ConnectedDominated Set (CDS). The process starts with graph G 200. A workinggraph, G′ is initiated where G′=G. The priority for nodes 210-224 isdesignated according to (degree, ID), wherein nodes with a higher degreehave a higher priority so that ties are broken by ID. Nodes 210-224start out by being relays to ensure full coverage at start-up. Each ofthe nodes 210-224 shares its 1-hop neighbor information with itsneighbors. The process then prunes down nodes from G′. If a node'sneighbors are neighbors, the node leaves the working graph G′. Nodescompute 2-hop cover set, wherein a node leaves the working graph G′ whenneighbor is not used to cover 2-hop neighbors. Each node receives itsneighbors' algorithm output indicating whether it should be part of theCDS and accepts only the output of the highest-priority neighbor, thatis, the highest priority nodes have the last word over their lowerpriority neighbors. Nodes 210-224 reach their eventual output within atmost two seconds in some embodiments in which convergence time is afunction of how often nodes exchange information. Thus, the SLAN networkachieves high capacity and fair access on the Long Link. Referring toFIG. 2, priority is determined according to (degree, node ID), wherein(2, .)>(1, .) and (2,3)>(2,1).

In FIG. 2, Node 1 210 has a degree of 2, Node 2 212 has a degree of 3,Node 3 214 has a degree of 3, Node 4 216 has a degree of 1, Node 5 218has a degree of 1, Node 6 220 has a degree of 2, Node 7 222 has a degreeof 3 and Node 8 224 has a degree of 1. Node 6(2) 220 computes its 2-hopcover set and finds node 7(3) 222 is used to cover 3(3) 214 and 8(1)224. Only 2-hop information is available. Node 3(3) 214 determinesinstead that node 7(3) 222 is to cover 6(2) 220 and 8(1) 224. Node 7(3)222 listens to Node 3(3) 214 because it has a higher degree than Node6(2) 220. Thus, the Nodes in the computed CDS are 1(2)-2(3)-3(3)-7(3).

FIGS. 3 a-f illustrates a downlink dissemination process 300 accordingto an embodiment. In FIG. 3 a-f, Nodes 0-6 310-322 are shown. Nodes knowthey are either download (DL)-connected () or DL-disconnected (x). Theconnected nodes closest to disconnected neighbors are favored forrobustness. Nodes are selected with the smallest number of hops to aDL-connected node. Ties are broken with connectivity information (numberof neighbors). Ties are further broken with active forwardinginformation. Ties are further broken by selecting node with lowest ID.Iteration is periodically performed to reach disconnected nodes morethan 1 hop away and to handle mobility.

In FIG. 3 a, Node 1, Node 3, Node 5 and Node 6 are DL-disconnected. Node0, Node 2 and Node 4 are DL-connected. In FIG. 3 b, Node 6 322 only hasdisconnected neighbors. Thus, Node 6 322 is not selected. Node 3 316 hasNode 4 318, i.e., 4(3), and Node 2 314, i.e., 2(2) as connectedneighbors. Node 4 318, 4(3), has a higher priority, i.e., 3>2, and isthus selected as a forwarder. Node 3 316 becomes 1-hop connected. InFIG. 3 c, Node 5 has Node 4 318, i.e., 4(3), as a connected neighbor.Thus, Node 4 318 is identified as a forwarder. Node 5 320 becomes 1-hopconnected.

In FIG. 3 d, for Node 1 310, the connected neighbors is made up of Node4 318, Node 2 314 and Node 0 310, i.e., [4(3), 2(2), 0(1)]. SinceNode 4 318 has a higher priority, 3>2>1, Node 4 318 is selected as aforwarder. Node 1 becomes 1-hop connected. In FIG. 3 e, Node 6 322 hasno DL-connected neighbors. Node 5, 320 is a 1-hop connected neighbor andis selected as a forwarder. Node 6 322 becomes a 2-hop connected node.Node 4 318 and Node 5 320 are traffic forwarders. FIG. 3 f illustratesthe final results, wherein Node 4 318 and Node 5 320 are trafficforwarders.

FIG. 4 illustrates packet scheduling 400 in a wireless networkperforming distributed beamforming according to an embodiment. In FIG.4, three nodes, N1 410, N1 412, N1 414, in a SLAN 402 are shown sendingpackets. The three nodes, N1 410, N1 412, N1 414, are also shown sendingdata on the Long Link 404. The Long Link 404 is divided in epochs 420and slots 430. However, the epochs 420 and slots 430 do not necessarilyreflect the actual time-division of the Long Link module. A packet isallocated to future epoch 420 to allow time for dissemination. Aconsistent time reference is used across beamforming nodes. The numberof slots 430 is allocated proportional to nodes' load. Mapping isdevised using the source node ID and the packet ID, e.g., {Src Node Id;Pkt Id} to specific future epoch/slot.

Equation 1 illustrates a formula for performing the mapping:

$\begin{matrix}{{{ts}_{i} = {{\left( {\left\lbrack \frac{t_{now} + {hD}}{\Delta \; N} \right\rbrack + 1} \right) \times \Delta \; N} + {n_{i}\Delta}}},} & (1)\end{matrix}$

where

$\left( {\left\lbrack \frac{t_{now} + {hD}}{\Delta \; N} \right\rbrack + 1} \right) \times \Delta \; N$

finds the epoch in the future (hD from now, where hD is the maximumdissenmination delay), and n_(i)Δ is the slot in that epoch with Δ beingthe slot time and N is the maximum nodes. Dynamic slot allocation andconflict resolution may also be implemented.

The uplink interface provides uplink hand-off by de-queuing one epoch ata time and reordering packets for that epoch to account fordissemination vagaries and transfers to the Long Link module. Thereceive time reference periodically stores t_(now) as offset to amonotonically increasing counter and adjusts the time offset.

To illustrate scheduling, slot assignments [1, 2, 3, 4, 5, 6, 7] areconsidered. For the illustration, the slot time, A, is equal to 50, themaximum disseminatin delay is 1000 and the maximum nodes is 7. Two nodeswith ID 2 and 6 schedule a packet at time t_(now)=5 according toequations 2 and 3:

$\begin{matrix}{{{{N_{2}:{ts}_{2}} = {{{\left( {{\frac{5 + 1000}{50 \times 7}} + 1} \right) \times 50 \times 7} + {2 \times 50}} = {{1050 + {2 \times 50}} = 1150}}};}{and}} & (2) \\{{N_{6}:{ts}_{6}} = {{{\left( {{\frac{5 + 1000}{50 \times 7}} + 1} \right)50 \times 7} + {2 \times 50}} = {{1050 + {6 \times 50}} = 1350.}}} & (3)\end{matrix}$

Accordingly, uplink dissemination according to an embodiment providesefficient multi-hop dissemination of single-sourced packets throughoutthe squad. Downlink dissemination according to an embodiment providesrobust dissemination of multiple-sourced packets in the squad network.Uplink scheduling according to an embodiment provides a slotted schedulefor packet transmissions on long link in the future, sender reservation.A priority rule uses node degrees to break ties using node ID for moreefficiency. A pruning process is used to better deal with initializingand partitioning.

The above detailed description includes references to the accompanyingdrawings, which form a part of the detailed description. The drawingsshow, by way of illustration, specific embodiments that may bepracticed. These embodiments are also referred to herein as “examples.”Such examples may include elements in addition to those shown ordescribed. However, also contemplated are examples that include theelements shown or described. Moreover, also contemplated are examplesusing any combination or permutation of those elements shown ordescribed (or one or more aspects thereof), either with respect to aparticular example (or one or more aspects thereof), or with respect toother examples (or one or more aspects thereof) shown or describedherein.

Publications, patents, and patent documents referred to in this documentare incorporated by reference herein in their entirety, as thoughindividually incorporated by reference. In the event of inconsistentusages between this document and those documents so incorporated byreference, the usage in the incorporated reference(s) are supplementaryto that of this document; for irreconcilable inconsistencies, the usagein this document controls.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one, independent of any otherinstances or usages of “at least one” or “one or more.” In thisdocument, the term “or” is used to refer to a nonexclusive or, such that“A or B” includes “A but not B,” “B but not A,” and “A and B,” unlessotherwise indicated. In the appended claims, the terms “including” and“in which” are used as the plain-English equivalents of the respectiveterms “comprising” and “wherein.” Also, in the following claims, theterms “including” and “comprising” are open-ended, that is, a system,device, article, or process that includes elements in addition to thoselisted after such a term in a claim are still deemed to fall within thescope of that claim. Moreover, in the following claims, the terms“first,” “second,” and “third,” etc. are used merely as labels, and arenot intended to suggest a numerical order for their objects.

The above description is intended to be illustrative, and notrestrictive. For example, the above-described examples (or one or moreaspects thereof) may be used in combination with others. Otherembodiments may be used, such as by one of ordinary skill in the artupon reviewing the above description. The Abstract is to allow thereader to quickly ascertain the nature of the technical disclosure, forexample, to comply with 37 C.F.R. §1.72(b) in the United States ofAmerica. It is submitted with the understanding that it will not be usedto interpret or limit the scope or meaning of the claims. Also, in theabove Detailed Description, various features may be grouped together tostreamline the disclosure. However, the claims may not set forthfeatures disclosed herein because embodiments may include a subset ofsaid features. Further, embodiments may include fewer features thanthose disclosed in a particular example. Thus, the following claims arehereby incorporated into the Detailed Description, with a claim standingon its own as a separate embodiment. The scope of the embodimentsdisclosed herein is to be determined with reference to the appendedclaims, along with the full scope of equivalents to which such claimsare entitled.

What is claimed is:
 1. A method for disseminating packets in a networkperforming distributed beamforming, comprising: distributing packetsfrom nodes in a local area network using a first interface and a firstwaveform to beamforming nodes; providing scheduling to a long linkinterface for delivering a stream of packets free of schedulingconflicts; and distributing a copy of the packets from a long linkinterface based on the provided scheduling and using a second waveform,the first waveform being different from the second waveform.
 2. Themethod of claim 1, wherein the distributing a copy of the packets from along link interface comprises distributing the copy of the packets froman uplink of the long link interface.
 3. The method of claim 2, whereinthe distributing the copy of the packets from an uplink of the long linkinterface comprises: identifying nodes in a network and an arrangementof the nodes; computing a second-hop cover set for a first node in anarrangement of nodes in the network; computing a second-hop cover setfor a second node in the arrangement of nodes in the network, whereinthe second-hop cover set for the first node and the second second-hopcover set for the second node includes at least one relay node forforwarding packets to a second-hop nodes in the first and secondsecond-hop cover set; determining a common node in the first and secondsecond-hop cover sets; determining whether the first node or the secondnode has a higher priority; and selecting the common node as a forwarderfor the first or second node determined to have the higher priority andremoving the first or second node determined not to have the higherpriority from the arrangement of nodes in the network.
 4. The method ofclaim 3, wherein the identifying, computing a second-hop cover set for afirst node, computing a second-hop cover set for a second node,determining a common node in the first and second second-hop cover sets,determining whether the first node or the second node has a higherpriority and selecting the common node as a forwarder are repeated foreach node iteratively to produce a resulting network arrangement.
 5. Themethod of claim 6, wherein the resulting network arrangement becomesstatic in a static network and continuously adapts to dynamic networks.6. The method of claim 1 further comprising initially arranging thenodes in the network as relays.
 7. The method of claim 6 furthercomprising pruning the nodes in the network as being relays to reach areduced set of forwarders to disseminate traffic to the nodes in thenetwork.
 8. The method of claim 1, wherein the distributing a copy ofthe packets from a long link interface comprises distributing the copyof the packets from a downlink of the long link interface.
 9. The methodof claim 8, wherein the distributing the copy of the packets from adownlink of the long link interface comprises: identifying connectedneighboring nodes for a node of interest; selecting connectedneighboring node with a highest priority as a forwarder; and when nodeof interest has no connected neighboring nodes, selecting a neighboringnode connected via multiple hops to a connected node as a forwarder. 10.The method of claim 9, wherein the identifying connected neighboringnodes, selecting connected neighboring node with a highest priority as aforwarder and selecting a neighboring node connected via multiple hopsto a connected node as a forwarder are repeated for each nodeiteratively until the selecting connected neighboring node with ahighest priority as a forwarder and selecting multi-hop disconnectedneighboring node as a forwarder becomes static for each node in a staticnetwork and continuously adapts to dynamic networks.
 11. The method ofclaim 10, further comprising pruning the nodes in the network as beingrelays to reach a reduced set of forwarders to disseminate traffic tothe nodes in the network.
 12. The method of claim 1, wherein theproviding scheduling to the long link interface for delivering a streamof packets free of scheduling conflicts comprises: dividing the longlink interface into epochs and slots allocating a number of slotsproportional to a load of a disseminating node; allocating packet to afuture epoch to allow time for dissemination; allocating packet to aslot in a distributed manner delivering a stream of ordered and timesynchronized packets mapping a source node identifier and a packetidentifier associated with an allocated packet to future epochs andslots; and providing a time reference across beamforming nodes.
 13. Themethod of claim 12, wherein the mapping a source node identifier and apacket identifier associated with an allocated packet to future epochsand slots is performed according to:${{ts}_{i} = {{\left( {\left\lbrack \frac{t_{now} + {hD}}{\Delta \; N} \right\rbrack + 1} \right) \times \Delta \; N} + {n_{i}\Delta}}},$where$\left( {\left\lbrack \frac{t_{now} + {hD}}{\Delta \; N} \right\rbrack + 1} \right) \times \Delta \; N$finds the epoch in the future, hD from now, where hD is a maximumdissemination delay, and n_(i)Δ is the slot in that epoch with Δ being aslot time and N is a maximum number of nodes.
 14. A network performingdistributed beamforming, comprising: a plurality of transmission nodesarranged in a network, the plurality of transmission nodes forming alocal area network; an intended node for receiving transmissions formthe plurality of transmission nodes; and a long link interface at theintended node for forming constructive interference from transmissionsfrom the plurality of transmission node, the long link interface beingprovided scheduling for a delivery of a stream packets free ofscheduling conflict; wherein the plurality of transmission nodes in alocal area network distributes packets using a first waveform to theintended node and distributing a copy of the packets via the long linkinterface using a second waveform, the first waveform being differentfrom the second waveform.
 15. The network of claim 14, wherein theplurality of transmission nodes distribute a copy of the packets via thelong link interface by distributing the copy of the packets using anuplink of the long link interface.
 16. The network of claim 15, whereinthe plurality of transmission nodes distributes the copy of the packetsby the uplink of the long link interface by: identifying nodes in anetwork and an arrangement of the nodes; computing a second-hop coverset for a first node in the arrangement of nodes in the network;computing a second-hop cover set for a second node in the arrangement ofnodes in the network, wherein the second-hop cover set for the firstnode and the second second-hop cover set for the second node includes atleast one relay node for forwarding packets to a second-hop nodes in thefirst and second second-hop cover set; determining a common node in thefirst and second second-hop cover sets; determining whether the firstnode or the second node has a higher priority; and selecting the commonnode as a forwarder for the first or second node determined to have thehigher priority and removing the first or second node determined not tohave the higher priority from the arrangement of nodes in the network.17. The network of claim 16, wherein the plurality of transmission nodesrepeat the identifying, computing a second-hop cover set for a firstnode, computing a second-hop cover set for a second node, determining acommon node in the first and second second-hop cover sets, determiningwhether the first node or the second node has a higher priority andselecting the common node as a forwarder for each node iteratively untilthe selecting the common node as a forwarder becomes static in a staticnetwork and continuously adapts to dynamic networks.
 18. The network ofclaim 14, wherein the plurality of transmission nodes distribute a copyof the packets via a long link interface by distributing the copy of thepackets from a downlink of the long link interface.
 19. The network ofclaim 18, wherein the plurality of transmission nodes distributes thecopy of the packets via the downlink of the long link interface by:identifying connected neighboring nodes for a node of interest;selecting connected neighboring node with a highest priority as aforwarder; and when node of interest has no connected neighboring nodes,selecting a neighboring node connected via multiple hops to a connectednode as a forwarder.
 20. The network of claim 19, wherein the pluralityof transmission nodes repeat the identifying connected neighboringnodes, selecting connected neighboring node with a highest priority as aforwarder and selecting one-hop disconnected neighboring node as aforwarder for each node iteratively until the selecting connectedneighboring node with a highest priority as a forwarder and selectingone-hop disconnected neighboring node as a forwarder becomes static in astatic network and continuously adapts to dynamic networks.
 21. Thenetwork of claim 14, wherein the long link interface scheduling for adelivery of a stream packets free of scheduling conflict is provided by:dividing the long link interface into epochs and slots allocating anumber of slots proportional to a load of a disseminating node;allocating packet to a future epoch to allow time for dissemination;allocating packet to a slot in a distributed manner delivering a streamof ordered and time synchronized packets mapping a source nodeidentifier and a packet identifier associated with an allocated packetto future epochs and slots; and providing a time reference acrossbeamforming nodes.
 22. The wireless network of claim 21, wherein thesource node identifier and the packet identifier associated with anallocated packet are mapped to future epochs and slots according to:${{ts}_{i} = {{\left( {\left\lbrack \frac{t_{now} + {hD}}{\Delta \; N} \right\rbrack + 1} \right) \times \Delta \; N} + {n_{i}\Delta}}},$where$\left( {\left\lbrack \frac{t_{now} + {hD}}{\Delta \; N} \right\rbrack + 1} \right) \times \Delta \; N$finds the epoch in the future, hD from now, where hD is a maximumdissemination delay, and n_(i)Δ is the slot in that epoch with Δ being aslot time and N is a maximum number of nodes.